<template>
    <ui-scrollbar ref="scrollContainer" :vertical="false" class="scroll-container" @wheel.native.prevent="handleScroll">
      <slot />
    </ui-scrollbar>
  </template>
  
  <script>
  const tagAndTagSpacing = 4 // 标签间距
  
  export default {
    name: 'ScrollPane',
    data() {
      return {
        left: 0
      }
    },
    computed: {
      scrollWrapper() {
        return this.$refs.scrollContainer.$refs.wrap
      }
    },
    mounted() {
      this.scrollWrapper.addEventListener('scroll', this.emitScroll, true)
    },
    beforeDestroy() {
      this.scrollWrapper.removeEventListener('scroll', this.emitScroll)
    },
    methods: {
      handleScroll(e) {
        const eventDelta = e.wheelDelta || -e.deltaY * 40
        const $scrollWrapper = this.scrollWrapper
        $scrollWrapper.scrollLeft = $scrollWrapper.scrollLeft + eventDelta / 4
      },
      emitScroll() {
        this.$emit('scroll')
      },
      moveToTarget(currentTag) {
        const $container = this.$refs.scrollContainer.$el
        const $containerWidth = $container.offsetWidth
        const $scrollWrapper = this.scrollWrapper
        const tagList = this.$parent.$refs.tag
  
        let firstTag = null
        let lastTag = null
  
        // 查找第一个标签和最后一个标签
        if (tagList.length > 0) {
          firstTag = tagList[0]
          lastTag = tagList[tagList.length - 1]
        }
  
        if (firstTag === currentTag) {
          $scrollWrapper.scrollLeft = 0
        } else if (lastTag === currentTag) {
          $scrollWrapper.scrollLeft = $scrollWrapper.scrollWidth - $containerWidth
        } else {
          // 查找上一个和下一个标签
          const currentIndex = tagList.findIndex(item => item === currentTag)
          const prevTag = tagList[currentIndex - 1]
          const nextTag = tagList[currentIndex + 1]
          const afterNextTagOffsetLeft = nextTag.$el.offsetLeft + nextTag.$el.offsetWidth + tagAndTagSpacing
          const beforePrevTagOffsetLeft = prevTag.$el.offsetLeft - tagAndTagSpacing
          if (afterNextTagOffsetLeft > $scrollWrapper.scrollLeft + $containerWidth) {
            $scrollWrapper.scrollLeft = afterNextTagOffsetLeft - $containerWidth
          } else if (beforePrevTagOffsetLeft < $scrollWrapper.scrollLeft) {
            $scrollWrapper.scrollLeft = beforePrevTagOffsetLeft
          }
        }
      }
    }
  }
  </script>
  
  <style lang="scss" scoped>
  .scroll-container {
    white-space: nowrap;
    position: relative;
    overflow: hidden;
    width: 100%;
    ::v-deep {
      .el-scrollbar__bar {
        bottom: 0px;
      }
      .el-scrollbar__wrap {
        height: 49px;
      }
    }
  }
  </style>
  